The present invention relates to sound spatialization with room effect.
The invention finds an advantageous but non-limiting application in the processing of sound signals respectively issuing from L channels associated with virtual speakers (for example in a multi-channel representation, or in a surround-sound representation, of the sound to be rendered), for spatialized rendering on real speakers (for example two earpieces of a headset in binaural rendering, or two separate speakers in transaural rendering).
For example, the signal from one of these channels can be processed to have a first contribution in the left earpiece and a second contribution in the right earpiece in binaural rendering, in particular by applying a transfer function with room effect to each of these contributions. The application of these transfer functions with room effect then contributes to providing the listener with a feeling of immersion, as if the virtual speaker associated with that channel is “positioned” relative to the listener.
In one particular embodiment, described in particular in document FR13 57299, a transfer function with room effect is applied to each sound signal of a corresponding channel in the time domain, in the form of a BRIR-type of impulse response (“Binaural Room Impulse response”). In particular, in that document which is incorporated herein by reference, the BRIR transfer function is constructed as a combination of:                a first transfer function specific to each signal, and        a second, general transfer function, common to all signals and characterizing in particular a reverberant field, the presence of the latter usually occurring in a room after a certain amount of time, typically after the first reflections of a sound wave.        
Such an embodiment advantageously allows applying processing common to all signals, which physically corresponds in actuality to a “blend” of acoustic waves as reverberations occur, therefore after a certain amount of time (characterizing the beginning of the presence of the reverberant field). Such an embodiment reduces the complexity of spatialization processing with room effect on multiple initial channels.
However, in modules with spatialization occurring prior to rendering, there is a desire to further minimize the complexity of spatialization processing. As a non-limiting example, the signals of the channels are received in encoded form by a compression decoder. This decoder sends the signals of the channels, once decoded, to a spatialization module for rendering the sound with room effect on two speakers. It is then desirable that the processing in this spatialization step (which follows the decoding of the received signals) be of reduced complexity so that it does not slow down all the decoding and spatialization steps when the signals are received prior to rendering.